A catalytic converter for a car uses a catalyst to convert, for example, three harmful compounds in car exhaust into less harmful compounds. The three harmful compounds include hydrocarbons in the form of unburned gasoline, carbon monoxide formed by the combustion of gasoline, and nitrogen oxide created when heat in the engine forces nitrogen in the air to combine with oxygen. There are two main structures used in catalytic converters—honeycomb and ceramic beads. Most automobiles today use the honeycomb structure. The honeycomb structure is housed in a muffler-like package that comes before the exhaust pipe. The catalyst helps to convert carbon monoxide into carbon dioxide, the hydrocarbons into carbon dioxide and water, and the nitrogen oxides back into nitrogen and oxygen.
Various methods of manufacturing the catalyst used in the catalytic converter exist in the art. FIG. 1A illustrates a first conventional method of manufacturing the catalyst. The first method is known as a one-dip process. At a step 105, micron-sized platinum (Pt) ions are impregnated into micron-sized alumina (Al2O3) ions, resulting in micro-particles. The micro-particles have platinum atoms on the alumina ions. At a step 110, a wash coat is made using micron-sized oxides that include pint size alumina and pint size silica (SiO2), a certain amount of stabilizers for the alumina, and a certain amount of promoters. At a step 115, the micro-particles are mixed together with the wash coat. At a step 120, a cylindrical-shaped ceramic monolith is obtained. A cross-section of the monolith contains 300-600 channels per square inch. The channels are linear square channels that run from the front to the back of the monolith. At a step 125, the monolith is coated with the wash coat. This can be achieved by dipping the monolith in the wash coat. As such, the channels of the monolith are coated with a layer of wash coat. At a step 130, the monolith is dried. The layer of wash coat has an irregular surface, which has a far greater surface area than a flat surface. In addition, the wash coat when dried is a porous structure. The irregular surface and the porous structure are desirable because they give a high surface area, approximately 100-250 m2/g, and thus more places for the micro-particles to bond thereto. As the monolith dries, the micro-particles settle on the surface and pores of the monolith. At a step 135, the monolith is calcined. The calcination bonds the components of the wash coat to the monolith by oxide to oxide coupling. The catalyst is formed. FIG. 1B illustrates a microscopic view 145 of a channel of the monolith 140 that is coated with the layer of wash coat 150 having platinum atoms 155.
FIG. 2A illustrates a second conventional method of manufacturing the catalyst. The second method is known as a two-dip process. At a step 205, a wash coat is made using micron-sized oxides that include pint size alumina and pint size silica, a certain amount of stabilizers for the alumina, and a certain amount of promoters. At a step 210, a cylindrical-shaped ceramic monolith is obtained. At a step 215, the monolith is coated with the wash coat such as via dipping. As such, the channels are also coated with a layer of wash coat. Typically, the layer of wash coat has an irregular surface which has a far greater surface area than a flat surface. FIG. 2B illustrates a microscopic view 250 of a channel of the monolith 245 coated with the layer of the wash coat 255. Returning to FIG. 2A, at a step 220, the monolith is dried. The wash coat when dried is a porous structure. At a step 225, the monolith is calcined. The calcination bonds the components of the wash coat to the monolith by oxide to oxide coupling. Micron-sized alumina oxides are then impregnated with micron-sized platinum ions and other promoters using a method that is well known in the art. Specifically, at a step 230, platinum is nitrated, forming salt (PtNO3). The PtNO3 is dissolved in a solvent such as water, thereby creating a dispersion. At step 235, the monolith is dipped into the solution. At a step 240, the monolith is dried. At a step 245, the monolith is calcined. The catalyst is formed. FIG. 2C illustrates another microscopic view 250′ of the channel of the monolith 245′ coated with the layer of wash coat 255′ having platinum atoms 260.
FIG. 3A illustrates a microscopic view 305 of a surface of the layer of the wash coat after calcination. Platinum atoms 310 are attached to oxygen atoms of the alumina. When exhaust gas goes through the catalytic converter, the platinum atoms 310 help reduce the harmful compounds by converting them into less harmful compounds. However, these various methods of manufacturing the catalyst used in the catalytic converter suffer from a number of shortcomings. For example, the platinum atoms 310 are not fixed to their bonded oxygen atoms of the alumina and are able to move around to other available oxygen atoms as illustrated in FIGS. 3B-3C. As the platinum atoms 310 move, the platinum atoms 310 begin to coalesce with other platinum atoms resulting in larger particles 315, as shown in FIG. 3D, and a more energetically favorable state. It is understood that as the platinum particles become larger, it detrimentally affects the catalyst since surface area of the platinum atoms decreases. In high temperature applications, such as in an aged catalytic converting testing, the movement of platinum atoms is magnified. In addition, since cost of platinum is extremely expensive, excessive use of platinum is unwanted.
The present invention addresses at least these limitations in the prior art.